Process of and apparatus for drying liquids



1931- F. H. DOUTHITT PROCESS OF AND APPARATUS FOR DRYING LIQUIDS FiledDec. 30, 1925 I- I I 'hi I I TH/TT byezwm/ 7* Arrv.

terial, and to make it possible to operate at a higher temperature thanheretofore has been Patented Oct. 27, 1931 PATENT OFFICE FRANK HOWARDDOU'THITT, OF CHICAGO, ILLINOIS PROCESS OF AND APPARATUS FOR DRYINGLIQUIDS Application filed December This invention relates to an improvedprocess and apparatus for the recovery of the solid contents of liquids,especially those whose solids melt at the practical working temperatureof desiccating apparatus. Examples of such solids are malt extract andcertain fruit juices which after having their terial instead of beingdelivered in finely divided condition tends to cohere in chunks or largemasses which are apt to clog the apparatus and are otherwiseunsatisfactor Again, in the desiccating of certain materia s containingalbuminoids or other constituents which are easily damaged by hightemperature, such as eggs, it is necessary, with the old apparatus andprocess, to operate at a considerably reduced temperature, which reducesthe capacity of the apparatus below a practical operating point.

One object of my invention is to provide a process and apparatus capableof desiccating the class of liquids above mentioned without theformation of chunks or masses of the mapracticable, without damaging theproduct.

Generally speaking, this is accomplished by providing a cool zone withinthe desiccating chamber in a manner which will be hereinafter described.The eflect is enhanced by the fact that dry air is introduced; also thatdry, cool air may be introduced at the delivery pipe; also that adisintegrator or pulverizer is provided for reducing to fine particlesany lumps or masses that may have passed out of the drying chamber.

'Another object of the invention is to provide means for creating astrong cyclonic flow of heated air having a downward trend which causesit to converge toward the bottom of the drying chamber whence it will bedeflected upward along the central axis of the chamber, pas;- the sprayissuing from the spray nozzle 30, 1925. Serial No. 78,313.

and on through the outlet duct .at the top of the chamber, thusthoroughly exposing the atomized liquid to the drying'efiect of the hotair.

I accomplish my object in the manner illus trated in the accompanyingdiagram, which shows a complete working apparatus, the same being shownchiefly in Vertical section.

In the form selected to illustrate the invention the desiccating chamberis cylindrical at the upper portion and converges downward and inward atthe lower portion. Heated air for drying the liquid is blown into itfrom the upper portion through nozzles 12 which slant obliquely downwardand inward into the chamber from the bustle pipe 14;. The latterconstitutes a duct for supplying heated air under pressure to the dryingchamber. It encircles the said chamber at the upper portion asillustrated. It has been found that this arrangement of the nozzles isespecially advantageous for it produces a cyclonic effect in which theair not only whirls around the vertical axis of the chamber but alsomoves downward into the Z5 converging portion of the chamber, whence itis deflected upwards along the central axis and passes out through theair outlet duct 16 which will be hereinafter again referred to. An airflow of this character has been found so to be most eflicient.

Heated air under pressure is supplied to the bustle pipe by heating andblowing apparatus shown at the upper right portion of the figure. In theform shown this con sists of a casing 18 containing heating coils 20.Air is blown through this casing past the coils by means of a blower 22of anyappropriate design. Located within the drying chamber 10 is aspray nozzle 24 which sprays or atomizes the liquid to be treated. Theliquid is supplied to this nozzle under pressure through'a pipe 26 whichis disconnectibly connected at its upper end by a coupling 28 to a pipe30 which leads from a force 9:! pump 32. The pipe 26 enters the dryingchamber through a stationary tube 36 and for sealing purposes has sleeve40 which seats at the lower end of the tube.

The outlet duct 16, previously mentioned, 00

leads from the closed upper portion of the liquid which is beingtreated. It commonly happens that this air carries with it a smallpercentage of the solids from the drying chamber, and in order torecover these the duct is not led directly to the atmosphere, but is ledpreferably to a recovering chamber 34. This recovery chamber is notparticularly concerned tion and as one very much like it is shown in theaforesaid Patent 1,078,848 it need not be here described in detail. Thesame is true of that portion of the apparatus which supplies the liquidto be treated to the force pump 32.

The drying chamber connects at the bottom with an outlet duct 42 whichleads to apparatus for delivering to a barrel or other receptacle (notshown). In the form illustrated this apparatus has two .collectingchambers 46, 48 connected in tandem, the upper one being connected to adelivery pipe 50 through which the powder is conveyed to the upperchamber 46 and a return or vent pipe 52, by which such powder as is notdeposited is returned to the lower end of the drying chamber.

.At the lower right portion of the figure I have shown apparatus 54interposedbetween duct 42 and duct 50 for pulverizing any cotu's ofv U.S. Letters Patent No. 1,392.656 except hering masses which may bereceived from the drying chamber,but this apparatus is optional and isnot intimately concerned with my present invention. Pulveri'zingapparathis kind is shown and described in that the fan at the right ofthe unit, discharging to duct 50, is not particularly 'dewith my presentinven'- any desired degree. The chilling of the air also has the 'efiectof condensing the moisture from the air and drying it and thus there isa double effect produced upon the material. It is reduced to alower-temperature and is commingled with air which is much dryer thanthe rest of the air in the drying chamber. Dampers 72 are providedinducts64 so that the flow through them may be controlled as theoperator sees fit.

A duct 74 leads from'the'duct 64 to the delivery duct 42 issuing fromthe bottom of the drying chamber. This is provided with a damper 7 6 forcontrolling the flow of cold air through it. The purpose of this is toprovide alternate means for chilling the v desiccated material as itleaves the drying scribed therein and cooperates in promoting the abovementioned return of undeposiied powder through the pipe 52 to. be againpassed to the collecting chamber 46 by way Q of the duct 50.

- I will now describe one of the novel features of the apparatus, by theaid of which -I have made it possible efiiciently to handle liquidswhich are-sticky at the temperature at gvhich. drying apparatus isusually operate Openings 60 are formed in the sides of the dryingchamber near the lower portion, these openings in the illustrated casebeing in the form of two horizontal rows of vertically arranged slotsspaced eqgli-distantly and leading from two wind oxes or bustle pipes 62which encircle the chamber and are supplied with cold air through-ducts64 leading from a casing 66. Th1s casing contains cooler pipes 68, pastwhich air is forced by means of a blower 70 of any appropriate design.The pipes 68 contain refrigerated brine or other cooling fluid, with theresult that as the air passes them it becomes chilled to chamber, toprevent cohesion and adhesion and to reduce the temperature of theproduct prior to its introduction into the final storage receptacle.Duct 74 may be used either by itself or in conjunction with the ducts 64supplying cool air to bustle pipes 62 and openings 60.

In .practice, let it be assumed that the pump 32 is forcing out throughthe spray nozzle 24, and that the blower 22 is forcing air past theheating coils 20 into the wind box 14. Let it also be assumed that theblower 70 is forcing air 'past the cooling coils 68 into the cold airducts the liquid to be treated 64. w The liquid to be treated issuesfrom a whorl or cyclonic effect is produced of special type, that is,one in which the flow is helically downward. This causes the air firstto hug the walls of the chamber, but as the chamber converges toward thebottom, and the air must ultimately escape, it is finally de flecte'dupward along the central axis of the chamber and ultimately out throughthe out let duct 16. This causes a veryintimate ex-- posure of theliquid particles to the air, with the result that the m0isture isextracted to a very high percentage of efficiency and the desiccatedmaterial descends toward the bottom of the chamber. Heretofore in actingupon liquids whose solid contents tend. to.

cohere at the ordinary temperature at which.

such apparatus is operated, cliucks or masses formed in the chamber. Italso adhered to the zone of the air jets issuing from the openings 60 inthe side walls of the chamber. This immediately reduces the temperatureof the particles to a point which keeps them hard and non-cohesive, theresult being that they neither adhere to each other nor to the sides ofthe chamber. Furthermore the effect of the air streams issuing from theopenings 60 is to blow the material away from the sides of the chamber,and hence they have a tendency to remain in the central portions of thechamber until they reach the bottom of the chamber or nearly so. Thus itbecomes practicable to treat liquids which would otherwise tend to clogthe apparatus and to collect inmasses with a resulting inferiority ofproduct.

Another result of the chilling of the air at the bottom-of the chamberis that it makes it practicable to operate the drying chamber at theusual high temperature employed for materials which when desiccated donot have much tendency to cohere. This, of course, makes for efliciencyand increases the capacity of the apparatus as a whole. This effect isenhanced by the fact that the air in becoming chilled also loses itsmoisture, and hence is dry as it comes into contact with the treatedmaterial. This of course promotes the drying as well as the coolingeffect on the product.

Still another advantage is that as the material remains for so short aperiod in contact with the highly heated air, and is so soon projectedinto the cool zone, it becomes practicable to operate upon albumens andsimilar materials, the quality of which deteriorates or the character ofwhich changes if sub ected for any appreciable period to atemperatureequal to that at which it is desirable to operate the apparatus forordinary materials. Still another advantage is this: Ord1nar1ly theproduct which is delivered from the drying chamber is at quite anelevated temperature, and frequently enters the barrel or other storagereceptacle in the same cond1t1on. This is frequently deleterious to theprodnet, as it tends to generate additional heat, and in fact in somecases spontaneous combustion has occurred. With my apparatus thedesiccated material becomes greatly reduced in temperature before itfinally leaves the apparatus, and consequently the danger of spontaneousheating in the final storage receptacle is avoided.

Having thus described my inventlon what I claim as new and desire tosecure by Letters Patent is:

,other end of said chamber, said chamber having its main gas outlet atits first named end providing for egress of gas internally of saidadvancing current, to thus cause said gas current to return to the firstnamed end of said chamber internally of its path of advancing movement,means for introducing substance to be treated substantially centrally ofsaid returning current of gas to pass outwardly therethrough and intosaid advancing spiral gas current to be advanced thereby toward the saidother end of said chamber, and means at the said other end of saidchamber providing for the egress of treated substance.

2. The method of treating substances which comprises producing alongitudinally advancing spiral current of treating gas, causing saidcurrent to return in the opposite longitudinal direction internally ofits path of advancing movement, introducing the substance to be treatedin finely divided condition substantially centrally of said returningcurrent of gas to pass outwardly therethrough and into said advancingspiral gas current, and Withdrawing treated substance adjacent the locusof reversal of movement of said gas current.

3. Substance treating apparatus comprising a treating chamber, means atone end of said treating chamber for directing treating gas into thesame in a circumferential and longitudinal direction to produce anadvancing spiral gas current traveling toward the other end of saidchamber, said chamber having its main gas outlet at its first named endproviding for egress of gas internally of said advancing current to thuscause said gas current to return to the first named end of said chamberinternally of its path of advancing movement, means at the said otherend of said chamber for introducing cooler gas and creating a cooledzone adjacent the locus of reversal of movement of said gas current, i

means for introducing substance to be treated substantially centrally ofsaid returning current of gas to pass outwardly therethrough and intosaid advancing spiral gas current to be advanced thereby to said cooledzone, and means providing for the egress of treated substance from saidcooled zone.

4. Substance treating. apparatus comprising a treating chamber, meansfor creating an advancing spiral current of treating gas travcling fromone end of said chamber toward the other end thereof, said chamberhaving its main gas outlet at its first named end providing for egressof gas internally of said advancing current to thus cause said gascurrent to return to the first named end of said chamber internally ofits path of advancing movement, means at the said other end of saidchamber for introducing cooler gas and creating a, cooled zone adjacentthe locus of reversal of movement of said gas current, means forintroducing substance to be treated substantially centrally of saidreturning current of gas to pass outwardly therethrough and into saidadvancing spiral gas current to be advanced thereby to said cooled zone,and means providing for the egress of treated substance from said cooledzone.

5. Substance treating apparatus comprisinga vertical treating' chamber,means at the top of said treating chamber for directing treating gasinto the same in a circumferential and longitudinal direction to producean advancing spiral gas current traveling toward the bottom of saidchamber, said chamber having its main gas outlet at its top providingfor egress of gas internally of said advancing current to thus causesaid gas current to return to the top of saidchamber in ternally of itspath of advancing movement, means at the bottom of said chamber forintroducing cooler gas and creating a cooled zone adjacent the locus ofreversalof movement of said gas current, means for introducing substanceto be treated substantially centrally of said returning current of gasto pass outwardly therethrough and into said advancing spiral gascurrent to be advanced thereby to said cooled zone, and means providingfor the egress of treated substance from said cooled zone.

6. Substance treating apparatus comprising a downwardly taperingvertical treating chamber, means for creatlng an advancing spiralcurrent of treating gas traveling from the top of said chamber towardthe bottom thereof, said chamber having its main gas outlet at its topproviding for egress of gas internally of said advancing current to thuscause said gas current to return to the top of said chamber internallyof; its path of advancing movement, means at the narrow end of saidchamber for introducing cooler gas and creating a cooled zone at thenarrow end thereof, means for introducing substance to 36 treatedsubstantially centrally of said returning current of gas to passoutwardly therethroughand into said advancing spiral gas current tobeadvanced thereby to said cooled zone andmeans providing for the egressof treated substance from said cooled zone adjacent the locus ofreversal'of move ment of said gas current, and introducing the substanceto be dried in finely divided condition substantially centrally o fisaidreturning current of gas to pass outwardly therethrough and into saidadvancing spiral gas current to be advanced thereby to said cooled zone.

8. The method of drying substances which comprises producing adownwardly advancing spiral current of drying gas, causing said currentto return upwardlyinternally of its path of downward movement, producinga cooled zone adjacent tothe locus of reversal of movement of said gascurrent, and introducing the substance to be dried in finely dividedcondition substantially centrally of said upwardly returning gas currentto pass outwardly therethrough and into said downwardly advancing spiralgas current to be carried downwardly thereby to said cooled zone.

9. Substance treating a paratus comprising a vertical chamber 0substantially circular cross-section,-means associated with the upperpart of said chamber providing for the lntroduction of a flow oftreating gas substantially tangentially thereof and its egresssubstantially centrally thereof to produce a cyclonic current of gasflowing generally from the periphery of said chamber toward the centerthereof, means associated with the lower portion of said chamber foradmitting an additional flow of treating gas to said vchamber to createa zone therein substantially excluding said first named flow and tothence progress toward the point of egress of said first named flow tomingle with and exit with the same, means for introducing the materialto be treated intothe mixed gases approaching sald point of egress topass outwardly therethrough into said first named flow and thence intosaid zone substantially excluding said first namedflow', andmeansproviding for the withdrawal of treated substance from said zone. I

10. The method of treating substances which comprises creating aninwardly flowing cyclonic current of treating gas in the upper part of atreating chamber and with drawing gas from the vortex thereof, creatinga flow of auxiliary treatin gas in the lower part of the treatingchamdmr substantlally excluding said first named treating gas from azone therein and flowing there from 1nto safid vortex to mingle with andbe withdrawn with said first named gas, introducing the substance to bedried substantially centrally of said vortex to pass outwardly through 7said mixed gases into said first named current and thence into said zonefrom lot which said 'first named gas is substantially excluded, andwithdrawing the treated sub- I stance from said zone.

11. Incombination a spray drying apparatus embodying. a drying chamberhaving a vmain drying zone and a zone to which the.

substantially dried particles pass therefrom, means for withdrawing astream of gas and particles from said last named zone, means forseparating the bulk of said particles from said stream, and means forreturning the unseparated particles to said last named zone withoutagain exposing them in said main drying zone.

12. Substance treating apparatus comprising a drying chamber providedwith a prod uct discharge at one end; and means for withdrawing a streamof gas and product from said product discharge, separating the bulk ofthe product therefrom, and reintroducing said stream and remainingproduct adjacent said product discharge end to mingle with the streambeing withdrawn therefrom.

13. Substance treating apparatus comprising a drying chamber providedwith a product discharge at one end; and means for withdrawing a streamof gas and product from said product discharge, mingling auxiliaryconditioning gas therewith, separating the bulk of the producttherefrom, and reintroducing said stream and remaining product adjacentsaid product discharge end to mingle with the stream being withdrawntherefrom.

14. Substance treating apparatus comprising a drying chamber ofgenerally circular cross-section decreasing toward its productdischargeend; means for creating a spiral current of drying gas advancing fromthe 7 larger end of the chamber toward its product discharge end; saidchamber having its main gas outlet at its first named end providing foregress of gas internally of said advancing current to thuscause said gascurrent to return to the first named end of said chamber internally ofits path of advancing movement, and means for withdrawing a stream ofgas and product from said product-discharge end, separating the bulk ofthe product therefrom, and reintroducing said stream adjacent saidproduct-discharge end.

15. Substance treating apparatus comprising a drying chamber ofgenerally circular cross-section decreasing toward-its productdischargeend; means for creating a spiral current of drying gas advancing fromthe larger end of the chamber toward its product-discharge end; saidchamber having its main gas outlet at its first named end providing foregress of gas internally of said advancing current to thus cause saidgas current to return to the first named end of said chamber internallyof its path of advancing movement; means for introducing auxiliary"conditioning gas adjacent said product-discharge end, and means forwithdrawing a stream of gas and product from said productdischarge end,separating the bulk of the product therefrom, and reintroducing saidstream adjacent said product-discharge end.

16. Substance treating apparatus comprising a drying chamber. ofgenerally circular cross-section decreasing toward its productdischargeend; means for creating a spiral current of drying gas advancing fromthe larger end of the chamber toward its productdischarge end; saidchamber having its main gas outlet at its first named end providing foregress of gas internally of said advancing current to thus cause saidgas current to return to the first named end of said chamber internallyof its path of advancing movement; means for introducing auxiliaryconditioning gas'adjacent said product-discharge end; and means forwithdrawing a stream of gas and product from said product-discharge end,mingling further auxiliary conditioning gas therewith, separating thebulk of the product therefrom and reintroducing said stream adjacentsaid product-discharge end.

17. The improvement in the art of separating a substance from a liquidcomprising the same which consists in spraying the liquid into a body ofhot drying gas to separate the substance as finely divided particles suspended in gas, cooling said suspended particles, segregating a stream ofgas and cooled suspended particles, separating the bulk of saidparticles from said stream, and returning and re-minglin g the remainingsuspended particles with other cooled suspended particles to bere-passed through the separating process therewith.

18. The improvement in the art of separating a substance from a liquidcomprising the same which consists in spraying the liquid into a body ofhot drying gas to separate the substance as finely divided particlessuspended in gas, creating a body of cooler gas to receive saidsuspended particles from said hot drying gas, withdrawing a stream ofsaid cooler gas and suspended particles and separating the bulk of saidparticles from said stream, and re-mingling the particles unseparatedfrom said stream with other particles in said body of cooler gas to berepassed through the separating process therewith.

In witness whereof, I have hereunto subscribed my name.

FRANK HOWARD DOUTHITT.

